1. Field
The present application relates to energy storage devices, and particularly to energy storage devices comprising frustules of diatoms.
2. Description of the Related Art
Diatoms typically include unicellular eukaryotes, such as single-celled algae. Diatoms are abundant in nature and can be found in both fresh water and marine environments. Generally, diatoms are enclosed by a frustule having two valves fitted together through a connective zone comprising girdle elements. Diatomaceous earth, sometimes known as diatomite, can be a source of frustules. Diatomaceous earth comprises fossilized frustules and can be used in a diverse range of applications, including as a filtering agent, a filling agent for paints or plastics, an adsorbent, cat litter, or an abrasive material.
Frustules often comprise a significant amount of silica (SiO2), along with alumina, iron oxide, titanium oxide, phosphate, lime, sodium, and/or potassium. Frustules are typically electrically insulating. Frustules may comprise a wide variety of dimensions, surface features, shapes, and other attributes. For example, frustules may comprise diverse shapes, including but not limited to cylinders, spheres, discs, or prisms. Frustules comprise a symmetrical shape or a non-symmetrical shape. Diatoms may be categorized according to the shape and/or symmetry of the frustules, for example grouping the diatoms based on existence or lack of radial symmetry. Frustules may comprise dimensions within a range from less than about one micron to about hundreds of microns. Frustules may also comprise varying porosity, having numerous pores or slits. Pores or slits of frustules may vary in shape, size, and/or density. For example, frustules may comprise pores having dimensions from about 5 nm to about 1000 nm.
Frustules may comprise significant mechanical strength or resistance to shear stress, for example due to the dimensions of the frustule, frustule shape, porosity, and/or material composition.